For some time, climate control systems for motor vehicles known from the prior art comprise coolant circuits with different individual components, such as the condenser which is traditionally arranged towards the front of the motor vehicle, the compressor linked to and driven by the vehicle engine, the evaporator arranged in the passenger compartment, as well as hoses and connections. The climate control system conditions the air which is subsequently fed into the passenger compartment. The compressor is normally driven by the engine of the motor vehicle by the input of mechanical energy to the compressor shaft. The electrical power for the radiator fan and the blower is supplied from the 12 V electrical power system of the motor vehicle.
The inlet air for the passenger compartment is sucked-in by means of the blower into the air-conditioning unit and is conducted across the evaporator for cooling and/or dehumidification. When the climate control system is operated in the refrigeration mode, heat is extracted from the vaporous coolant compressed in the compressor at a high pressure level, which is discharged into the ambient air.
When the condenser is installed in the frontal area of the motor vehicle, it stands vertical to the direction of airflow and normally has a large mesh surface, which in smaller motor vehicles has values in the range of 14 dm2 to 18 dm2, in motor vehicles of the compact class values in the range of 20 dm2 to 22 dm2, and in the larger motor vehicles values above 24 dm2.
The mesh surface is to be understood as the surface which essentially stands vertically aligned relative to the direction of flow of the air at the inlet and/or at the outlet of the heat exchanger, which is also described as flow surface. For this purpose, the mesh surface comprises the ribbed area or the area of the heat exchanger which is designed with ribs and corresponds to the flow area on the air-side.
Radiator fans designed as axial flow fans are used for conveying the ambient air through the heat exchanger, which are arranged as suction fans on the air discharge side of a so-called radiator module. While the axial fans convey a large air volume flow although at a low pressure differential, the heat exchangers of the refrigeration module, which are arranged sequentially in one row and are flowed through on the air-side, such as the coolant/air heat exchanger of the engine coolant circuit, the intercooler and the condenser of the coolant circuit are designed as shallow as possible to reduce the flow resistance of the air, however. Being shallow is to be understood as the thickness of the heat exchanger in the direction of airflow and/or the length of the flow on the air-side.
In the prior art, climate control systems for motor vehicles were operated in the heat pump mode using ambient air as a heat source, the heat exchangers are used as evaporators when operated as condensers in the refrigeration mode.
During the operation of the heat exchangers, with which heat is discharged from the coolant into the ambient air in the refrigeration mode and heat is absorbed from the ambient air in the heat pump mode, the ambient air is sucked by means of the radiator fan or a radiator fan package through the heat exchanger. Without any additional air velocity based on the motor vehicle velocity, that is when the motor vehicle is not in motion, only small average airflow velocities of up to 3.5 m/s are attained during maximum radiator fan output.
However, the airflow velocity has a significant influence on the power that can be absorbed from the ambient air without icing of the heat exchanger and therefore on the heating capacity of a heat pump, using ambient air as a heat source. Because of the arrangement of the radiator fan in the airflow direction downstream of the heat exchanger known from the prior art, the waste heat being generated in the drive of the radiator fan is moreover not usable.
An air volume less than 600 kg/hr. is traditionally applied on the heat exchanger when operated as evaporator in the refrigeration mode. On the other hand, a significantly higher air volume of more than 1800 kg/hr. flows through the heat exchanger when operated as condenser in the refrigeration mode and as evaporator in the heat pump mode.
Climate control systems with heat pump functionality are also known from the prior art, in which the evaporator is operated as evaporator both in the refrigeration mode as well as in the heat pump mode and the condenser is likewise operated as condenser both in the refrigeration mode as well as in the heat pump mode. In this context, the control of the heat flows is completely realized by controlling the flow on the air-side.
FR 2 743 027 A1 discloses a motor vehicle climate control system with a traditional coolant circuit, comprising merely an evaporator, a compressor, a condenser, and an expansion device. The heat exchangers are arranged in separate flow ducts, which are designed so that they are at least separate from one another in terms of flow technology. The flow ducts have interconnections or bypasses. The air mass flows sucked-in by means of blowers are conducted through the bypasses as required and depending on the operating mode, and are conducted across the surfaces of the heat exchangers by closing and opening of dampers. For this purpose, the air mass flows are cooled and/or dehumidified and/or heated and are subsequently discharged into the passenger compartment and/or into the environment.
DE 10 2011 052 752 A1 describes a modular motor vehicle climate control system for heating and cooling of air. The motor vehicle climate control system comprises a housing with a blower and dampers for the adjustment of airflow paths as well as a coolant circuit with a condenser, an evaporator, a compressor, and expansion device and associated connection lines. An evaporator/airflow path with an integrated evaporator and a condenser/airflow path with an integrated condenser are formed in the housing. Fresh air from the environment, recirculated air from the passenger compartment, or a mixture of both can be supplied to each airflow path. Both airflow paths are interconnected by means of controllable dampers such that the heating or cooling of the passenger compartment is done simply by adjusting the flow path of the air.
Control strategies for preventing icing of the evaporator during operation in the heat pump mode are furthermore known from the prior art. In this context, the power consumption in the evaporator is limited depending on the ambient temperature, such as by means of the temperature level and/or by means of the vapor pressure of the coolant.
DE 10 2011 051 285 A1 discloses a method and a device to control the prevention of icing for an evaporator of a heat pump of climate control systems in motor vehicles. The passenger compartment is heated using a heat pump comprising the evaporator, which uses ambient air as a heat source for evaporating liquid coolant. The thermal velocity of the ambient air is controlled based upon the temperature of the ambient air upstream of the evaporator, utilizing the device to control the prevention of icing. For control, the surface temperature of the evaporator is estimated or calculated by means of measuring signals for pressure and temperature of the coolant flowing in the coolant line in a section of the coolant line between the outlet of the evaporator and the inlet of the compressor, the dewpoint of the ambient air ahead of the motor vehicle is determined, the flow velocity of the ambient air and the temperature level of the evaporator surface is adjusted by means of the aperture cross-section of the expansion device, the coolant mass flow in the coolant line and the rotational speed of the fan is adjusted depending on the number of strokes or the rotational speed of the compressor, depending on the type of compressor. In addition, minimal superheating is specified on the evaporator to prevent localized icing of the evaporator.